NFC: make AtomicOrdering an enum class

Summary:
In the context of http://wg21.link/lwg2445 C++ uses the concept of
'stronger' ordering but doesn't define it properly. This should be fixed
in C++17 barring a small question that's still open.

The code currently plays fast and loose with the AtomicOrdering
enum. Using an enum class is one step towards tightening things. I later
also want to tighten related enums, such as clang's
AtomicOrderingKind (which should be shared with LLVM as a 'C++ ABI'
enum).

This change touches a few lines of code which can be improved later, I'd
like to keep it as NFC for now as it's already quite complex. I have
related changes for clang.

As a follow-up I'll add:
  bool operator<(AtomicOrdering, AtomicOrdering) = delete;
  bool operator>(AtomicOrdering, AtomicOrdering) = delete;
  bool operator<=(AtomicOrdering, AtomicOrdering) = delete;
  bool operator>=(AtomicOrdering, AtomicOrdering) = delete;
This is separate so that clang and LLVM changes don't need to be in sync.

Reviewers: jyknight, reames

Subscribers: jyknight, llvm-commits

Differential Revision: http://reviews.llvm.org/D18775

llvm-svn: 265602

1 files changed, 5 insertions, 5 deletions

diff --git a/llvm/lib/Target/Sparc/SparcISelLowering.cpp b/llvm/lib/Target/Sparc/SparcISelLowering.cpp
index ebb77924324..b0fa6a19a9a 100644
--- a/llvm/lib/Target/Sparc/SparcISelLowering.cpp
+++ b/llvm/lib/Target/Sparc/SparcISelLowering.cpp
@@ -2929,12 +2929,12 @@ static SDValue LowerUMULO_SMULO(SDValue Op, SelectionDAG &DAG,
 }
 
 static SDValue LowerATOMIC_LOAD_STORE(SDValue Op, SelectionDAG &DAG) {
-  // Monotonic load/stores are legal.
-  if (cast<AtomicSDNode>(Op)->getOrdering() <= Monotonic)
-    return Op;
-
-  // Otherwise, expand with a fence.
+  if (isStrongerThanMonotonic(cast<AtomicSDNode>(Op)->getOrdering()))
+  // Expand with a fence.
   return SDValue();
+
+  // Monotonic load/stores are legal.
+  return Op;
 }
 
 SDValue SparcTargetLowering::